In the filling industry and in particular the industry dealing with filling of liquid products into individual packages, it is desirable to provide accurate control of the actual volume of liquid product being filled. For this it has proven to be efficient to make use of filling valves wherein a control command allows opening of the valve. Hence, liquid product is discharged and a closing command makes sure that the filling valve is closed when a predetermined volume has been discharged.
Filling valves provide a number of advantages with regards to e.g. availability, controlling, and compactness. However it is necessary to accurately determine the performance of the filling valves in order to control the operation. Since opening and closing is performed by moving a valve member between two positions there will be some discharging during these moving sequences whereby a certain amount of liquid will be allowed to escape through the filling valve and thus such volume will contribute to the total volume being discharged.
In order to accurately control the operation of the filling valves a flow meter may be provided, which flow meters are configured to transmit a pulse each time a predetermined volume passes an associated flow meter. By counting the number of pulses from the flow meter it is possible to determine the accumulated volume passing through the flow meter. Hence, once the filling valve is commanded to open the flow meter will start to measure the volume being discharged. When a certain volume has been discharged the filling valve will be commanded to close whereby a controller assumes an additional volume to be added to the discharged volume due to the delay in the closing operation of the filling valve. However, should the actual closing operation of the filling valve differ from the assumed operation for some reason the total volume of discharged liquid will deviate from the desired volume. This provides a drawback for the filling operator since the individual packages may contain too much or too less liquid if the closing operation of the filling valve is affected in some way.
Hence, it is necessary to provide a method for a filling valve, as well as a filling valve system, resulting in a more accurate control of the filling valves.